05621412 is referenced by 375 patents and cites 13 patents.

A system and method which conserves energy in the operation of a transponder or tag (14) by providing that the transponder (14) be enabled or awakened in multiple stages. A threshold detector (62) is provided which measures the power level of received RF energy. If the RF energy received by the detector (62) exceeds a pre-determined level, the transponder (14) then employs a modulation detector (64) to ascertain whether it has been awakened by a valid interrogation signal from an interrogator (12) or whether the RF energy received was merely a spurious burst of RF energy from some other source. If a pre-determined modulation is detected by the modulation detector (64), the transponder (14) is then fully activated to its normal operational state.

Title
Multi-stage transponder wake-up, method and structure
Application Number
233839
Publication Number
5621412
Application Date
June 7, 1995
Publication Date
April 15, 1997
Inventor
Mark A Hamlett
Garland
TX, US
Dwaine S Hurta
Garland
TX, US
Claude A Sharpe
McKinney
TX, US
Agent
Richard L Donaldson
James C Kesterson
Rebecca A Mapstone
Assignee
Texas Instruments Incorporated
TX, US
IPC
G07B 15/00
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